No antioxidant beneficial effect of zinc supplementation on oxidative stress markers and antioxidant defenses in middle-aged and elderly subjects: the Zenith study.

OBJECTIVE: The aim of the study was to investigate whether zinc supplementation affects antioxidant status in European middle-aged and elderly people. DESIGN: Multicentre prospective intervention study, randomized, double-blind, placebo-control. SETTING: France (Clermont-Ferrand/Theix, and Grenoble), Italy (Rome), Northern Ireland (Coleraine). SUBJECTS: A total of 387 healthy middle-aged (55-70 yrs) and free-living older aged (70-85 yrs) subjects were randomly allocated to three groups: 0, 15 or 30 mg zinc gluconate/d in addition to usual dietary intake during 6 months. METHODS: Oxidative stress status was evaluated by measurement of protein oxidation (plasma thiol groups), lipid peroxidation (plasma thio-barbituric acid reactants, TBARS), whole blood glutathione levels, erythrocyte copper/zinc superoxide dismutase activity and plasma antioxidant status (ferric reducing antioxidant power assay), at baseline and after 3 and 6 months. RESULTS: Zinc supplementation did not alter oxidative stress markers and antioxidant defenses in elderly, after 3 or 6 months, except an increase in Cu/Zn superoxide dismutase activity. CONCLUSIONS: In apparently healthy free living elderly people, a single zinc supplementation had no effects on oxidative stress status.

Age- and sex-dependent effects of long-term zinc supplementation on essential trace element status and lipid metabolism in European subjects: the Zenith Study.

Given the key role of Zn in many physiological functions, optimal Zn status could be a predictive parameter of successful ageing. However, the benefit of Zn supplementation is still a matter of debate since Zn supplementation has been reported to be associated with the alteration of Cu status and lipid metabolism. As part of the Zenith Project, the present study aimed to investigate, in free-living healthy European middle-aged and older subjects, the effect of Zn supplementation on the biochemical status of Zn, Fe and Cu and on lipid profile. Volunteers aged 55-70 (n 188) and 70-85 (n 199) years old participated in a double-blinded, randomised study and received a daily placebo, or Zn as 15 or 30 mg for 6 months. Zn supplementation did not significantly modify erythrocyte Zn levels or erythrocyte Cu,Zn-superoxide dismutase activity. But Zn supplementation at 15 or 30 mg/d for 6 months increased significantly serum Zn levels and Zn urinary excretion with no major adverse effects on Fe and Cu status or on lipid metabolism. However, Zn supplementation at 30 mg/d showed some age- and sex-dependent alterations in Fe status or lipid profile. Therefore, with respect to the key role of an optimal Zn status in successful ageing, Zn supplementation at 15 mg/d, when necessary, could be safely proposed regarding lipids and the risk of interaction with Fe and Cu.